cosmos stubbornly refuses to bloom

I haven't planted cosmos in several years. I planted the dwarf variety 3
years ago, and have just enjoyed the chance reseeding (the dwarf variety
seems to reseed a bit less prolifically than the taller varieties). This
year, I have many plants of various sizes, from 6 inches to about 2 feet
tall, all of which have been blooming for the past month or more - however,
I have one plant which has a huge healthy central stalk, numerous strong
healthy branches, and not only no flowers, but not a single flower bud. It
is about 2 1/2 feet tall by now, less than a foot from other cosmos which
have been blooming for weeks. I would say that the central stalk on the
non-blooming cosmos is nearing 2 inches in diameter, and is practically
becoming woody. Since we sometimes have a killing frost in mid-September,
I'm starting to think that I won't see a single flower off that plant. Has
anyone else had that kind of a cosmos experience?

After composting and soil improvement in my yard for the past 25 years
I can't grow cosmos either, my soil is too rich.
Cosmos prefer poor soil to bloom well- but I bet you have a ton of
pretty foliage.

I don't have the answer, but I got a cosmos just like the one you describe
in a batch I bought on closeout from a garden center. All the others in the
pack grew nicely. The one just turned into a huge bushy weed. I noticed it
seemed a bit hairier than the ones that flowered, though the leaves were
similar enough.
I pulled it out to give the others more room.
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I've had the same experience. One year I had cosmos plants that grew huge
but wouldn't flower. I tried adding flower fertilizer, Potassium something
I think it was, and breaking off the roots near the plant, but they would
not bloom.
I agree with the idea that the soil is too rich. When I first started my
garden and the soil was poor, cosmos flowered well. Now my soil is
enriched. However, the year mine wouldn't flower, I looked around the city
and saw other gardens in which the cosmos was flowering poorly, so I'm not
certain of my explanation, maybe it was just the weather.

I planted some a few years ago, they were great. I don't think they have
ever rebloomed. My job ended June 30 and I've spent more time in the
gardens this summer, and I have a ton of little plants, all 12" or less,
and no blooms. I purposely didn't weed them out thinking I'd have a mass
of colorful blooms this summer.
We do have good soil but that doesn't explain why they bloomed the first
year and never again, does it?
Diane
Zone 6

Diane, cosmos are annuals, so I wouldn't expect them to rebloom - only to
self-sow themselves so that a new generation could bloom the following year.
I'm wondering how you have little seedlings around if the cosmos hasn't
bloomed the past few years....

Damned if I know! Maybe I should take a pic. But they sure loke like
little Cosmos plants. I thought it was my moonbeam spreading *way* out
but they are a bit different. I think I have the good camera with me so
I'll grab a pic and send you the link later.
Thanks!
Diane

The pic could be cosmos foliage - it's hard to tell with the ends weighted
down with water. I suppose it's possible that some seeds survived
underground for several years and germinated when the soil was disturbed,
although I wouldn't normally think of cosmos seeds as being that persistent.
(Usually hard-coated seeds like grains and beans seem to have a longer
"shelf-life".) There are a few other plants with very fine thread-like
foliage, including nigella. Have you ever planted that? (Just thinking out
lout).
anyone?

No, it doesn't sound or look familiar. Sorry, I didn't think about the
water. That area gets full souther sun against a white house and my
dryer vents nearby. However last winter was pretty hard and I almost
lost all my roses, so I would be surprised as well if they lasted
Considering it's September I guess I'll rip them out and plant real ones
next year. I really liked them.
Oh, I do have a Coreopsis Moonbeam nearby but it doesn't look *quite*
the same as that.
Thanks,
Diane

Any plant has the ability to re-seed, if it makes seeds. Since 'Moonbeam' is a
hybrid, it may have re-seeded, but did not have the characteristics of the
'Moonbeam.'
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http://old-homes.net/pix/ours/flowers03/IMG_1040.jpg
I really should take another.
Anyway, it never gets more than 6" tall and is only in this one garden
(and has been).
When pulling some today I notices the bottoms of the stems were usually
black.
I'll take some pix and start another thread.
Thanks!
Diane

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